London's network of closed-circuit TV (CCTV) cameras may help investigators track down those responsible for the terrorist bomb attacks Thursday, which have left more than 50 people dead and several hundred injured, police said Friday.
"There are a large number of CCTV tapes we need to seize and to review," said Andy Hayman, assistant commissioner of the Metropolitan Police, at a televised news conference Friday morning.
Several thousand video cameras monitor London's Underground and mainline rail stations, and many more are perched high above streets and shopping centers. They are seen primarily as a way to deter muggings, street brawls and other antisocial behavior, and to monitor the build-up of crowds on railway platforms.
The cameras were never intended as a deterrent against terrorist attacks, but they may help investigators to figure out where and when the explosive devices were planted Thursday, and potentially to identify suspects, said a representative from a U.K. consulting company that provides security services to London's transport authorities.
"In terms of terrorism, their primary value at the moment is for post-incident analysis," said the representative, who asked that his company not be identified.
The usefulness of CCTV cameras depends on how they are deployed, said Robert Wint, a spokesman for Verint Systems UK, which provides some of the equipment for the Underground's CCTV system. In most cases the cameras film continuously, he said, meaning investigators should be able to review footage for clues.
Police declined to say Friday if the cameras located where the bombs went off were working or exactly how much film footage they have to review.
The network of cameras has earned the U.K. something of a Big Brother reputation, and civil liberties groups have decried their use as an invasion of privacy. However, some Britons may be more inclined now to give up some privacy if it means protection from terrorism.
"We should consider all means, including detention without trial, house arrest and ID cards, if there is a chance that we may make this a safer place," said one letter writer in the U.K.'s Guardian newspaper Friday.
Forensic evidence gathered at the scene will also be key to the investigations, U.K. Home Secretary Charles Clarke said in an interview with the BBC Thursday. "We are looking for a small number of evil needles in a very big haystack,'' he said. Members of the public who saw anything suspicious are also urged to call the U.K. police anti-terrorist hot line.
British Prime Minister Tony Blair has said the blasts were likely the work of Islamic terrorists. A group purporting to be related to the al Qaeda terrorist network claimed responsibility Thursday, although its involvement has still not been confirmed.
Initial forensic work suggests that devices packed with less than 10 pounds of explosives were left on the floor of each of the three trains, and on the floor or the seat of the bus, police said Friday. There is still no evidence that the bus attack was a suicide bombing, police said, though they have not ruled out the possibility.
Authorities considered shutting down London's cellular phone networks after the blasts but decided against it, believing mobile phones did not pose a threat.
"We did consider it because we do have that capability," Metropolitan Police Commissioner Sir Ian Blair said at the news conference Friday morning.
They decided not to close the networks because people were relying on mobile phones to communicate with family and loved ones, he said.
Investigators in the Madrid train bombings last year have said cell phones were used to trigger the blasts there.
Many people turned to text messaging and e-mail instead to share news of the disaster. The volume of e-mail traffic in Europe doubled in the hours after the blast, according to security company MessageLabs. Blogging company Technorati said its search engine was swamped Thursday by people looking for postings related to the attacks.
"The bombings in London today have had a huge impact across the world's weblogs," it said on its site.
Digital cameras and cell phones provided a way to share pictures and video as the events unfolded. Television news channels ran grainy video footage taken by a cell phone as injured passengers filed out of a tunnel near King's Cross station, while Reuters ran an image of injured victims at Tavistock Place, where the bus exploded, also taken by a cell phone user.
More than 50 people were killed in the attacks, Commissioner Blair said Friday. There were also around 700 people injured. Of those, 350 went to hospitals, and 100 were kept in overnight.